The present invention relates to a metal mold arrangement for casting a cylinder block of a water-cooled engine, and more particularly, to a type thereof used in a horizontal type casting machine where the cylinder block can be molded in its vertical orientation with a cylinder bore portion surrounded by a water jacket being positioned up and a crank chamber being positioned down during casting. Throughout the specification, the "horizontal type casting machine" implies the machine where a casting sleeve and a mold cavity are positioned on the horizontal plane.
Japanese Patent Application Kokai No. Hei 1-178361 discloses a method and apparatus for casting a cylinder block having a water jacket for use in a water-cooled type internal combustion engine. The disclosed invention uses a horizontal type casting machine where a metal mold is disposed so that the cylinder block extends horizontally. That is, as shown in FIG. 8, a stationary die 103 is fixed to a stationary platen 1, and a movable die 104 fixed to a movable platen 2 through a die base 14 is disposed in confronting relation to the stationary die 103.
In the stationary die 103, a stationary die 105 extends toward the movable die 104 for supporting a cast iron sleeve 23 which serves as a cylinder liner and for defining a crank chamber. That is, the stationary die 105 is provided so that a resultant cylinder block extends horizontally. To this effect, a bore pin 129 which defines a cylinder bore integrally protrudes horizontally from the stationary die 105. The cast iron sleeve 23 is disposed over an outer peripheral surface of the bore pin 129. The stationary die 105 has a gate 105a in communication with a casting sleeve 19 which extends through a stationary platen 1 and the stationary mold 105. A bushing 20 is disposed over a portion of the casting sleeve 20, the portion being positioned at a side of the stationary die 105. A plunger chip 21 is slidably disposed in the casting sleeve 19.
A movable die 106 is disposed in the movable die 104. An ejector pin 118' and a water jacket core support pin 118 extend through and are movable relative to the movable die 106. One end of the ejector pin 118' is fixed to an ejector plate 15 movable along a pair of guide rods 16 extending in a die base 14. The ejector plate 15 is connected to a push rod 17 driven by a driving means not shown. Thus, in accordance with the movement of the ejector plate 15 along the guide rods 16 because of the movement of the push rod 17, the ejector pin 118' extends through the movable die 106 and protrudes toward the stationary die 103. Consequently, casted product can be removed from the metal mold. One end of the core support pin 118 is connected to a driving mechanism 118A. Because of the operation of the driving mechanism 118A, the core support pin 118 moves in an axial direction thereof.
An upwardly movable core 108 and a downwardly movable core 109 are movably disposed between the stationary die 103 and the movable die 104 for surrounding the stationary die 105 and the bore pin 129. Thus, a cavity is provided by a space defined by the stationary die 105, the bore pin 129, the upwardly movable core 108, the downwardly movable core 109 and the movable die 106.
Within the cavity, a water jacket core 122 is disposed concentrically around the cast iron sleeve 23 supported by the bore pin 129. A projection 122a radially outwardly extends from an outer peripheral surface of the water jacket core 122, and an upper surface of the downwardly movable core 109 is formed with a recess 109a at a position engageable with the projection 122a. Further, a lower surface of the upwardly movable core 108 is formed with an abutment face 108a abuttable on the water jacket core 122. The water jacket core 122 is held at a predetermined position in the cavity by the abutment between the abutment face 108a and the water jacket core 122 and the engagement between the recess 109a and the projection 122a.
The water jacket core supporting pin 118 has a free end extendible into and retractable from the cavity so as to temporarily hold the water jacket core 122 at a predetermined position up to the closure of the metal molds. For example, in case of a four cylinder in line engine shown in FIG. 9, the water jacket core supporting pin 118 is moved to extend from the movable die 106, so that the free ends of the pins 118 are positioned immediately below joining portions 122b of neighboring cylinders.
To be more specific, while the metal molds is open, the cast iron sleeve 23 is disposed around the bore pin 129 of the stationary die 105. Then, the driving mechanism 118A is operated so as to extend the water jacket core supporting pin 118 toward the stationary die, so that the water jacket core 122 is mounted on the free end of the pin 118. Next, the upwardly movable core 108 is moved to its descent position, and the downwardly movable core 109 is moved to its ascent position. Thus, the projection 122a of the water jacket core and the recess 109a are engaged with each other, and the abutment face 108a is brought into abutment with the water jacket core 122. Thus, the water jacket core 122 is fixed at a position.
Then, the movable die 104 is moved toward the stationary die 103 for closing the metal molds. The water jacket core 122 is thus disposed around the outer periphery of the sleeve 23. The mold closure provides a cavity for casting a cylinder block. Consequently, a water-cooled type cylinder block having a water jacket is produced by filling molten metal into the cavity by way of the injection sleeve 19.
In the above described conventional casting apparatus, the water jacket core 122 is temporarily held by the water jacket core support pin 118 until the metal molds are closed, and the water jacket core 122 is fixed at a position by the abutment between the water jacket core 122 and the abutment face 108a and by the engagement between the projection 122a and the recess 109a, so that the water jacket core 122 is positioned around the sleeve at the time of closure of the metal molds, Accordingly, it would be difficult to stably position the water jacket core 122 at a given position.
Further, since gas in the water jacket core 12 and the cavity has a nature of moving upwardly, thickness of the casted cylinder block at its upper portion is likely to be non-uniform by the elevating gas due to the horizontal orientation of the casted cylinder block. Gas defects such as misrun, cold shut and blow hole is likely to occur. Moreover, if boss portion is provided at an upper portion of the cavity, gas accumulation may occur at the boss portion. Furthermore, since the cylinder block is oriented horizontally, sufficient fluidity of the molten metal may not provided, and horizontal orientation in the solidifying direction results. Thus, non-uniform casting may occur particularly in case of laminar flow casting. Consequently, desirable product may not be obtainable.